Authentic Lessons for 21st Century Learning

Doggos, Digestion, and Fossils, Oh My!

Digestion and the Fossil Record

Heather Shaffery, Christiana Johnson | Published: July 18th, 2022 by K20 Center

  • Grade Level Grade Level 6th, 7th, 8th
  • Subject Subject Science
  • Course Course
  • Time Frame Time Frame 2-3 class period(s)
  • Duration More 150 minutes

Summary

Students will explore the relationship between the fossil record and the digestive system using coprolites (i.e., fossilized poop) as a phenomenon. By investigating the chemical and physical processes of digestion and connecting these to prior knowledge of fossil formation, students will explain what coprolites can tell us about the diet of the organisms they came from. Further exploration of scientific data behind the fossil phenomenon helps students draw conclusions about ecosystem-level interactions. This lesson addresses portions of MS-LS1-7, MS-LS4-1, and MS-LS4-2.

Essential Question(s)

How can we use fossils to learn about ancient organisms' diets and ecosystems?

Snapshot

Engage

Students view museum images of fossilized wild dog coprolites and construct initial explanations for how it’s possible for us to know how the dogs hunted based only on those fossils.

Explore

Students investigate the process of digestion using a physical model.

Explain

As a class, students discuss how waste products from digestion can provide information about an organism's diet and explain why this evidence is rare in the fossil record.

Extend

Using data from the scientific paper about the wild dog coprolites, students match the scientists' conclusions about the dogs' ecosystem to evidence that supports these claims. In addition, students provide scientific reasoning to justify the way they matched up the scientists' evidence and conclusions.

Evaluate

Students create a model to explain how digestion can produce the type of evidence found in the wild dog coprolites and why that evidence is useful for understanding ancient ecosystems.

Materials

  • Lesson Slides (attached)

  • CER Explanations handout (attached; one per student)

  • Digestion Model Student Guide (attached; one per student)

  • Digestion Model Teacher Guide (attached)

  • Model Observation Notes handout (attached; one per student)

  • The Digestive System handout (attached; one per student)

  • Evidence and Conclusions handout (attached; one per student)

  • Digestive System Model handout (attached; one per student)

  • Scissors (one pair per small group)

  • Gallon plastic bags (one per small group)

  • Metal trays (one per small group)

  • Plates/trays/dishes (one per small group)

  • Small and large plastic cups (one small and one large per small group)

  • Paper cups (one per small group)

  • Nylon "legs" (pantyhose) (one pair per small group)

  • Food samples (seeds, popcorn kernels, raisins, bananas, crackers, etc.) (one per small group)

  • Orange juice (one cup per small group)

  • Water (one cup per small group)

Engage

Display slide 5 to introduce the essential question: How can we use fossils to learn about ancient organisms' diets and ecosystems? Display slide 6 to introduce the lesson objectives to the students.

Display slide 7. As a formative assessment, ask students to explain what they know about poop. Use the Collective Brain Dump strategy to structure this conversation. Arrange students into small groups and encourage them to collaborate with their groups to share knowledge. When groups seem to be done sharing with one another, have each group share their knowledge with the whole class. As groups share, list items on the board to create a whole-class product. Using the whole-class list, you can guide the lesson to address misconceptions and gaps in knowledge. Example questions that generate interesting discussion on this topic include:

  • What is poop?

  • Why do we poop?

  • Where does poop come from?

Display slide 8. Show students images of the coprolites from the Natural History Museum of LA County. Tell them that scientists were able to figure out how the "bone-crushing" dogs hunted based on these fossils.

Display slide 9. Give students the CER Explanations handout (attached). Students should now begin to build a Claim, Evidence, Reasoning (CER). Ask them to write an initial explanation for how it was possible for scientists to draw that conclusion.

Explore

Provide students the materials and Digestion Model Student Guide (attached) for conducting the digestion model simulation. A Digestion Model Teacher Guide is also included in the attachments. Having students work in pairs is useful for this activity if the class is sufficiently small.

Student groups demonstrate the digestion model. Despite the messy ingredients, the pie pan and plates make clean-up for the investigation easy. With rare exception, clean-up only involved the students' normal post-lab procedure of wiping down their stations with a disinfecting wipe or spray cleaner.

Depending on class size and student responsibility, it may be helpful to have the entire class go through the activity at the same pace. The YouTube video “Lesson Idea: Digestive System Experiment” provides a clear demonstration of the entire model. If necessary, it can be used to help students (or teacher) assemble and use the model. If showing the video to the entire class, consider pausing between steps to ensure students are able to recreate each part of the model. A teacher demonstration of any portion of the model should not be used as a substitute for students doing the activity.

Display slide 12. Pass out the Model Observation Notes handout (attached). As students explore the model, they should record observations of what they see happening at each step on their Model Observation Notes handout, including what the food materials look like before and after they enter each section. If using the demonstration format, the observing students could record the information and let the demo students copy it down later. Several groups should have "undigestible" materials in their food that all students should have a chance to observe. Ask students to Carousel around the room to observe the final products of each group's model. They should record additional observations about their peers' models and attempt to identify the content of the "waste" products. After the Carousel, have students clean up their lab stations, using slide 13 for any class-specific instructions. 

Explain

Give students the Digestive System handout (attached). Display slide 14. As a class, ask students to describe what happened in each step of the model. Display slide 15. For each step, ask them to describe what part of their body the process is occurring in. (What organ does this part of the model represent? What process in digestion does this part of the model represent?) Display slide 16. Next, ask students where they think chemical reactions are happening in the system. Have them justify their claims based on prior knowledge and what they observed in the model.

After the group discussion, provide students a formal explanation of the digestive system using slides 17 through 20. While it's important to cover the entire system, focus more heavily on the structures and processes students misunderstood or left out during the conversation. Additional notes on each structure and process can be found in the Speaker Notes of the Lesson Slides.

If they already know part of the content, a brief overview is all that is necessary for those details. Include in the discussion:

  • organs

  • enzymes (students don't need to remember the specific names, just the purpose)

  • processes

  • places where chemical reactions occur

Display slide 21. Once students have a complete understanding of digestive processes, return to their observations from the Explore Carousel. Ask them to describe what they were able to identify in the "waste" products of the models. Help students connect this to their understanding of how fossils form. Some guiding questions to help facilitate this include:

  • What types of materials are most/least likely to fossilize?

  • Why are coprolites rare?

  • When poop does fossilize, what sort of materials might be found inside? Why?

Additionally, interesting conversation synthesizing content can be facilitated through student-generated questions. Student questions may include:

  • Why can't we eat our poop?

  • Why do some animals eat their poop?

Display slide 23. Have students brainstorm the types of conclusions they might be able to draw about an animal based on what they might find in its poop (e.g., whole seeds would tell us that animals can't digest that food).

Extend

Display slide 24. Remind students that scientists figured out how the "bone-crushing" dogs hunted based on their coprolites. Ask them to revise their explanation on the CER Explanations handout for how this is possible using what they now understand about digestion.

Display slide 25. Have students read about the scientific research on the "bone-crushing" dogs. Some options for readings include this Massive Science article titled “What can ancient dog poop reveal about an ecosystem?” or this NHMLA article titled “The Proof Is in the Pooping.” Alternatively, this article from Newsela titled describes how scientists use coprolites more generally. Discuss the article(s) as a class to help students determine why bones and other materials are left behind during digestion (e.g., lack of necessary enzymes, too dense for body to break down physically, etc.).

Display slide 26. Provide students with the Evidence and Conclusions handout. It contains the evidence scientists found within the coprolites and the specific things they concluded about the "bone-crushing" dogs' ecosystem. Ask students to match the evidence and conclusions by deciding what evidence supports each conclusion and explain why using what they understand about digestion and fossils. Note that pieces of evidence can be used to support more than one conclusion and conclusions may be supported by more than one piece of evidence. Display slide 27. After students complete the task, have them compare their answers and reasoning with a partner. They should discuss why their ideas do or do not match one another using the evidence and their learning so far.

Students may generate questions which provide an opportunity for a discussion connecting previous knowledge and the content learned during the lesson. The following questions may be particularly useful for reinforcing conceptual understanding of both the process of fossilization and chemical reactions during digestion, respectively:

  • Why is poop less likely to fossilize?

  • Why do poop and gas smell?

Evaluate

Display slide 28. Have students explain how the process of digestion left bone fragments in the coprolites of "bone-crushing" dogs. Provide the students with the Digestive System Model handout for them to use as part of their explanation.

In addition, students should revise their Engage/Extend explanation one more time to describe why scientists can use materials found in coprolites to understand ancient ecosystems. They should structure their final explanation as a CER, using evidence from the lesson to support their claim.

Display slide 29. Use the Muddiest Point strategy to close the lesson. Ask the students "What is your muddiest point about how we can use fossils to learn about ancient organisms' diets and ecosystems?" Use student responses to address any remaining misconceptions or wonderings.

Resources